Sir Henry was nominated, and sat as one of the judges who tried Charles I, but he with some courage or address escaped signing the death sentence, and afterwards claimed that he only accepted nomination in hopes of saving the King. Throughout the Commonwealth he remained Keeper of the Jewel House, though there were no jewels to guard, for these had been broken up, defaced, destroyed, and sold by the order of Parliament. But being one skilled in the etiquette of courts, he made himself useful as Master of Ceremonies to Foreign Ambassadors, and continued to enjoy the rich perquisites attaining to the office of Keeper of the Jewel House. For forty years Sir Henry Mildmay had grown fat and prosperous on the proceeds of his office; indeed, he became a very rich man with great estates and much ready cash to spend. But in 1660 Charles II was restored to the throne, and Sir Henry Mildmay was immediately pounced upon to produce the crowns and robes, sceptres, and jewels belonging to the kingly dignity, of which he was the reputed guardian. At the time the general impression was that Sir Henry had appropriated these to his own purposes and sold them to his own advantage; he was in consequence dubbed “the Knave of Diamonds.” As however has since become clear the royal emblems, or such as remained, were disposed of under the orders of Parliament. It may, however, be conjectured that Sir Henry, in accordance with the usages of the age and the rights of his office, secured a goodly percentage on the sale prices. His detractors averred that he had himself valued and bought in the Crown Jewels at the exceedingly low prices they fetched, and at his leisure disposed of them at great profit. There is, however, no recorded proof of this. But Sir Henry Mildmay, whether he had a guilty conscience or not, thought discretion the better part of valour, and attempted to escape abroad. He was, however, caught by Lord Winchelsea at Rye in Essex and sent back to London. He was tried in 1661 at the Bar of the House of Commons, and sentenced to be degraded from all his honours and titles. Furthermore, he was sentenced to be annually drawn on a hurdle through the streets of London from the Tower to Tyburn, then passed under the gallows, and again dragged back to the Tower. This penalty was to be exacted on each anniversary of the day on which sentence had been passed on Charles I, that is January 27th. Whether Sir Henry ever took this ride is not clear, but probably he did more than once, for it was only in 1664 that the Lords in mitigation ordered him to be transported to Tangiers. On the way to his exile, however, he died at the town of Antwerp. His vast accumulations of wealth were forfeited to the Crown, his estate at Wanstead being of sufficient importance to be assigned to James, Duke of York.